The number of U.S. senators supporting marriage equality increased to 53 on Friday after same-sex marriage endorsements from Democratic Sens. Joe Donnelly (Ind.), Heidi Heitkamp (N.D.).

In a post on his Facebook page, Donnelly noted previous pro-gay positions, including support for the repeal of “Don’t Ask, Don’t Tell” and support for LGBT workplace protections, as leading him to reconsider his stance on same-sex marriage:

“In recent years, our country has been involved in an important discussion on the issue of marriage equality. While serving in the House of Representatives, I had the opportunity to act on a core belief of mine: we are a stronger country when we draw on the strengths of all Americans. I voted to repeal ‘don’t ask, don’t tell’ and was an original supporter of the bill that would make it illegal to discriminate against someone in the workplace because of their sexual orientation. It is also for that reason that I oppose amending either Indiana’s or our nation’s constitution to enshrine in those documents an ‘us’ and a ‘them,’ instead of a ‘we.’ With the recent Supreme Court arguments and accompanying public discussion of same-sex marriage, I have been thinking about my past positions and votes. In doing so, I have concluded that the right thing to do is to support marriage equality for all.”

In a statement, Heitkamp said marriage equality was a matter of fairness:

“In speaking with North Dakotans from every corner of our great state, and much personal reflection, I have concluded the federal government should no longer discriminate against people who want to make lifelong, loving commitments to each other or interfere in personal, private, and intimate relationships. I view the ability of anyone to marry as a logical extension of this belief. The makeup of families is changing, but the importance of family is enduring.”

According to BuzzFeed, the two first-term senators discussed the issue personally and coordinated their statements to be released at the same time. Yesterday, Sen. Bill Nelson (D-Fla.) announced his support for marriage equality.

Following today’s joint endorsement from Donnelly and Heitkamp (N.D.) there are now only four Democratic members of the Senate who have not voiced their support for marriage equality: Tim Johnson (S.D.), Mary Landrieu (La.), Joe Manchin (W.Va.) and Mark Pryor (Ark.). On the other side of the aisle, only Republican Sens. Rob Portman (Ohio) and Mark Kirk (Ill.) have endorsed marriage equality.

[Photos: Joe Donnelly (right) and Heidi Heitkamp (Courtesy of the U.S. Senate)]

Justin Snow is Metro Weekly's former political editor and White House correspondent. Follow him on Twitter @JustinCSnow.